1. Field of the Invention
This invention relates to a method and apparatus for optical data transmission between two electrically separated transmitting-receiving units in which transmitting-receiving units have the following features which are that each of the transmitting-receiving units has at least one data transmitter and one data receiver and the first transmitting-receiving unit has a light transmitter for transmission of light energy and the second transmitting-receiving unt has a light receiver for receiving the transmitted light energy and also includes means for converting the light energy into electrical energy and includes means for storing the electrical energy for power purposes.
In a preferred embodiment in the optical bidirectional data transmission equipment such as electric lock systems, one of the two transmitting-receiving untis expediently the key is constructed as a small maintenance free unit. The use of a battery as an internal power supply contradicts this desired object for one of the transmitting-receiving units as it requires that the discharged and dead battery be changed and also makes it necessary to monitor the charged condition of the battery.
So as to be completely independent of the battery, it is desirable to provide an external power supply for one of the transmitting-receiving units expediently the lock, and this external power supply can be constructed with photocells which receive light energy.
A problem arises that both the data as well as the energy for the power supply of the one tansmitting-receiving unit are transmitted with light. Given a data receiver and energy receiving photo element that are spaced closely together, the data information can be in error due to blooming whereby errors result in the data transmission and great accuracy can no longer be assured.
2. Description of the Related Art
German Patent No. 0.075,701, European patent Application No. 0.053,790, U.S. Pat. No. 4,091,734, European Patent No. 0,103,790 and Patent Abstracts of Japan, Vol. 10, No. 386 E-4672443 of Dec. 24, 1986 entitled "Feed Transmission System Using Optical Fiber" all disclose various data transmitting systems of which the disclosures are hereby incorporated by refernce.